scholarly journals Effects of Continuous and Pulsed Ultrasonic Treatment on Microstructure and Microhardness in Different Vertical Depth of ZL205A Castings

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4240
Author(s):  
Gang Lu ◽  
Yisi Chen ◽  
Qingsong Yan ◽  
Pengpeng Huang ◽  
HongXing Zhan ◽  
...  
Keyword(s):  
Ultrasonic Treatment ◽  
Boundary Segregation ◽  
Propagation Distance ◽  
Solute Redistribution ◽  
Sampling Depth ◽  
Grain Sizes ◽  
Ultrasound Propagation ◽  
Solidification Interface ◽  
Pulsed Ultrasonic ◽  
Refinement Effect

In this paper, in order to improve the performance of the ZL205A castings, continuous ultrasonic and pulsed ultrasonic treatments were applied to the melted alloy to study the effect of ultrasound propagation distance on microstructure and microhardness. The results indicated that ZL205A grains were significantly refined by ultrasonic vibration, but the refinement effect became weak gradually with the increase of sampling depth. The minimum grain sizes were 103.2 μm and 122.5 μm respectively in continuous and pulsed ultrasonic treatment. Grain boundary segregation also became more serious and coarser with the increase of vertical depth. In addition, microhardness and vertical depth are not positively correlated linearly. As the vertical depth increased, microhardness first decreased and then increased, the maximum hardnesses were 73.9 HV and 72.84 HV, respectively, in the two process modes. According to the experiment results and available studies, the mechanism of ultrasonic treatment maybe that: the cooling rate of solidification interface front increased by cavitation and streaming, thus changing the solute redistribution behavior of the ZL205A melt.

An atom probe tomography study of grain boundary segregation in nanocrystalline Ni-W

2005 ◽  
Vol 903 ◽  
Author(s):  
Andrew Detor ◽  
Michael K. Miller ◽  
Christopher A. Schuh
Keyword(s):  
Grain Boundary ◽  
Atom Probe Tomography ◽  
Boundary Segregation ◽  
Atom Probe ◽  
Solute Segregation ◽  
Grain Boundary Segregation ◽  
Distribution Analysis ◽  
Grain Sizes ◽  
Composition Fluctuations ◽  
20 Nm

AbstractAtom probe tomography is used to observe the solute distribution in electrodeposited nanocrystalline Ni-W alloys with three different grain sizes (3, 10, and 20 nm) and the results are compared with atomistic computer simulations. The presence of grain boundary segregation is confirmed by detailed analysis of composition fluctuations in both experimental and simulated structures, and its extent quantified by a frequency distribution analysis. In contrast to other nanocrystalline alloys, the present Ni-W alloys exhibit only a subtle amount of solute segregation to the intergranular regions. This finding is consistent with quantitative predictions for these alloys based upon a thermodynamic model of grain boundary segregation.

Effect of Al-5Ti-B Refiner on Microstructure of Al-5Cu Aluminum Alloy

2011 ◽  
Vol 365 ◽  
pp. 89-93
Author(s):  
De Quan Shi ◽  
Yang Shao ◽  
Gui Li Gao ◽  
Zhi Wei Gao ◽  
Xu Dong Wang
Keyword(s):  
Aluminum Alloy ◽  
Holding Time ◽  
Experimental Results ◽  
Optimal Parameters ◽  
Fine Needle ◽  
Grain Sizes ◽  
Holding Temperature ◽  
Precipitation Phase ◽  
Refinement Effect

By using the Olympus GX71 microscope, the effects of Al-5Ti-B addition, holding time and holding temperature on the microstructure of Al-5Cu alloy have been studied, and the influencing rules have been got. The experimental results show that the refinement effect of Al-5Ti-B is very remarkable and the grain sizes of Al-5Cu become small. The optimal parameters are as follows. The refiner addition is 2%-3%, and the holding time is 15 minutes, and the holding temperature is 720°C-740°C. When the 2%-3% Al-5Ti-B refiner is added, the Al3Ti is fine needle shape and the precipitation phase Al2Cu is round flake shape or reticular shape. Simultaneously, the dendrites have minimum spacing, and the microstructure becomes fine and uniform.

Solidification interface transformation and solute redistribution of FeCrAl stainless steel

2017 ◽  
Vol 114 (4) ◽  
pp. 409 ◽  
Author(s):  
Jianhua Liu ◽  
Xiaofeng Su ◽  
Hongbo Liu ◽  
Zhibiao Han ◽  
Yang He ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Solute Redistribution ◽  
Solidification Interface

Influence of Ultrasonic Vibration on Grain Refinement of Pure Aluminum

2014 ◽  
Vol 898 ◽  
pp. 19-22
Author(s):  
Chun Li ◽  
Da Li ◽  
Yan Ping Ren ◽  
Jia Meng Qin
Keyword(s):  
Grain Refinement ◽  
Ultrasonic Vibration ◽  
Ultrasonic Treatment ◽  
Treatment Time ◽  
Pure Aluminum ◽  
Vibration Effect ◽  
Power Ultrasonic ◽  
Refinement Effect

In this paper, samples were prepared by power ultrasonic on molten Al ingot. The results show that microstructure of the samples treated by untrosonic vibration is more finer than that of the untreated ones, the ultrasonic treatment time is not the longer the better. When the vibration head dipped into the middle of the melton, the better grain refinement effect can be gotten. Too deep or too shallow of the vibration head dipped in, vibration effect just limited to near the head, the influence is relatively small when the melton far away from the vibration head.

Revealing the effect of grain boundary segregation on Li ion transport in polycrystalline anti-perovskite Li3ClO: a phase field study

2020 ◽  
Vol 22 (5) ◽  
pp. 3030-3036 ◽  
Author(s):  
Kun Shen ◽  
Yixuan Wang ◽  
Jun Zhang ◽  
Yi Zong ◽  
Gengwei Li ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Ion Transport ◽  
Field Study ◽  
Phase Field ◽  
Boundary Segregation ◽  
Effective Diffusivity ◽  
Grain Boundary Segregation ◽  
Negative Contribution ◽  
Grain Sizes ◽  
Li Ion

Phase field calculated effective diffusivity Deff of Li vacancy in anti-perovskite Li3OCl is shown as a function of average grain sizes. Li vacancy segregation reinforces the negative contribution of grain boundaries on the overall Li diffusion.

scholarly journals Effect of Coil Configuration Design on Al Solidified Structure Refinement

Metals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 153
Author(s):  
Jing Zhao ◽  
Ji-hao Yu ◽  
Ke Han ◽  
Hong-gang Zhong ◽  
Ren-xing Li ◽  
...  
Keyword(s):  
Structure Refinement ◽  
Experimental Results ◽  
Configuration Design ◽  
Coil Design ◽  
Grain Sizes ◽  
Refinement Effect

This paper outlines our effort to optimize PMO (Pulsed Magneto-Oscillation) design in order to improve the efficiency of ingot manufacturing. SPMO-H (Simplified Surface Pulse Magneto-Oscillation) and CPMO-H (Simplified Compound Pulse Magneto-Oscillation) were presented on the basis of SPMO (Surface Pulse Magneto-Oscillation) and CPMO (Compound Pulse Magneto-Oscillation). Our numerical and experimental results showed that optimized PMO coil design offered us a device that enabled the operator to examine and operate the melt more convenient without losing the efficiency and decreasing refinement effect. Our work also showed the distance between the coil and the melt surface had little effect on the grain sizes refined. Therefore, in ingot production, the dropping of melt surface is not a problem for PMO application.

Solute redistribution during in-situ irradiation of alloys in the high voltage electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 370-371
Author(s):  
P. R. Okamoto ◽  
N.Q. Lam ◽  
R. L. Lyles
Keyword(s):  
Electron Microscope ◽  
High Voltage ◽  
Driving Forces ◽  
Solute Diffusion ◽  
Solute Redistribution ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
High Voltage Electron ◽  
Thin Foils ◽  
Solute Atoms

During irradiation of thin foils in a high voltage electron microscope (HVEM) defect gradients will be set up between the foil surfaces and interior. In alloys defect gradients provide additional driving forces for solute diffusion since any preferential binding and/or exchange between solute atoms and mobile defects will couple a net flux of solute atoms to the defect fluxes. Thus, during irradiation large nonequilibrium compositional gradients can be produced near the foil surfaces in initially homogeneous alloys. A system of coupled reaction-rate and diffusion equations describing the build up of mobile defects and solute redistribution in thin foils and in a semi-infinite medium under charged-particle irradiation has been formulated. Spatially uniform and nonuniform damage production rates have been used to model solute segregation under electron and ion irradiation conditions.An example calculation showing the time evolution of the solute concentration in a 2000 Å thick foil during electron irradiation is shown in Fig. 1.

Grain boundary segregation in metals

1992 ◽  
Vol 50 (2) ◽  
pp. 1204-1205
Author(s):  
C.L. Briant
Keyword(s):  
Fracture Surface ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Material Properties ◽  
Electron Spectroscopy ◽  
High Vacuum ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Local Concentration ◽  
The One

Grain boundary segregation is the process by which solute elements in a material diffuse to the grain boundaries, become trapped there, and increase their local concentration at the boundary over that in the bulk. As a result of this process this local concentration of the segregant at the grain boundary can be many orders of magnitude greater than the bulk concentration of the segregant. The importance of this problem lies in the fact that grain boundary segregation can affect many material properties such as fracture, corrosion, and grain growth.One of the best ways to study grain boundary segregation is with Auger electron spectroscopy. This spectroscopy is an extremely surface sensitive technique. When it is used to study grain boundary segregation the sample must first be fractured intergranularly in the high vacuum spectrometer. This fracture surface is then the one that is analyzed. The development of scanning Auger spectrometers have allowed researchers to first image the fracture surface that is created and then to perform analyses on individual grain boundaries.

EELS Measurement of the Local Electronic Structure of Copper Atoms Segregated to Aluminum Grain Boundaries

1996 ◽  
Vol 54 ◽  
pp. 342-343
Author(s):  
S.J. Splinter ◽  
J. Bruley ◽  
P.E. Batson ◽  
D.A. Smith ◽  
R. Rosenberg
Keyword(s):  
Electronic Structure ◽  
Grain Boundaries ◽  
Boundary Segregation ◽  
Thin Layers ◽  
Nominal Composition ◽  
Spatially Resolved ◽  
Service Lifetime ◽  
Heat Treated ◽  
Probe Size ◽  
Local Electronic Structure

It has long been known that the addition of Cu to Al interconnects improves the resistance to electromigration failure. It is generally accepted that this improvement is the result of Cu segregation to Al grain boundaries. The exact mechanism by which segregated Cu increases service lifetime is not understood, although it has been suggested that the formation of thin layers of θ-CuA12 (or some metastable substoichiometric precursor, θ’ or θ”) at the boundaries may be necessary. This paper reports measurements of the local electronic structure of Cu atoms segregated to Al grain boundaries using spatially resolved EELS in a UHV STEM. It is shown that segregated Cu exists in a chemical environment similar to that of Cu atoms in bulk θ-phase precipitates.Films of 100 nm thickness and nominal composition Al-2.5wt%Cu were deposited by sputtering from alloy targets onto NaCl substrates. The samples were solution heat treated at 748K for 30 min and aged at 523K for 4 h to promote equilibrium grain boundary segregation. EELS measurements were made using a Gatan 666 PEELS spectrometer interfaced to a VG HB501 STEM operating at 100 keV. The probe size was estimated to be 1 nm FWHM. Grain boundaries with the narrowest projected width were chosen for analysis. EDX measurements of Cu segregation were made using a VG HB603 STEM.

Reflection electron microscopy of as-grown diamond surfaces

1993 ◽  
Vol 51 ◽  
pp. 1006-1007
Author(s):  
Z.L. Wang ◽  
J. Bentley ◽  
R.E. Clausing ◽  
L. Heatherly ◽  
L.L. Horton
Keyword(s):  
Electron Microscopy ◽  
Synthetic Diamond ◽  
High Energy ◽  
Dark Field ◽  
Reverse Direction ◽  
Diamond Surfaces ◽  
Grain Sizes ◽  
Synthetic Diamonds ◽  
De Beers ◽  
Reflection Electron Microscopy

It has been found that the abrasion of diamond-on-diamond depends on the crystal orientation. For a {100} face, the friction coefficient for sliding along <011> is much higher than that along <001>. For a {111} face, the abrasion along <11> is different from that in the reverse direction <>. To interpret these effects, a microcleavage mechanism was proposed in which the {100} and {111} surfaces were assumed to be composed of square-based pyramids and trigonal protrusions, respectively. Reflection electron microscopy (REM) has been applied to image the microstructures of these diamond surfaces.{111} surfaces of synthetic diamond:The synthetic diamonds used in this study were obtained from the De Beers Company. They are in the as-grown condition with grain sizes of 0.5-1 mm without chemical treatment or mechanical polishing. By selecting a strong reflected beam in the reflection high-energy electron diffraction (RHEED) pattern, the dark-field REM image of the surface is formed (Fig. 1).

Sign in / Sign up

Export Citation Format

Share Document